Slick MappedTo[String] 列不能像这样使用

Question

我想使用 MappedTo[String] 作为一种列类型。有一个查询使用like来选择一些记录。

示例代码：

case class ID(value: String) extends scala.slick.lifted.MappedTo[String]

class Order(tag: Tag) extends Table[(ID, String)](tag, "order") {
  def id = column[ID]("id", O.PrimaryKey)
  def name = column[String]("name", O.NotNull)
  def * = (id, name)
}

val ordres = TableQuery[Order]

def all(implicit session: Session) = {
  ordres.filter(_.id like "2014.%").list
}

编译器错误：

[error]  value like is not a member of scala.slick.lifted.Column[models.ID]
[error]     ordres.filter(_.id like "2014.%").list
[error]                        ^
[error]  ambiguous implicit values:
[error]  both value BooleanColumnCanBeQueryCondition in object CanBeQueryCondition of type => scala.slick.lifted.CanBeQueryCondition[scala.slick.lifted.Column[Boolean]]
[error]  and value BooleanOptionColumnCanBeQueryCondition in object CanBeQueryCondition of type => scala.slick.lifted.CanBeQueryCondition[scala.slick.lifted.Column[Option[Boolean]]]
[error]  match expected type scala.slick.lifted.CanBeQueryCondition[Nothing]
[error]     ordres.filter(_.id like "2014.%").list

如何解决？谢谢。

Answer 1

我目前找到的唯一解决方案是求助于sql interpolated strings

//slick needs this to be able to convert to your custom wrapper type
implicit val GetID = GetResult(r => ID(r.nextString))

def all(implicit session: Session) = {
  sql"""select id, name from order where id like '2014.%'""").list
}

---

作为旁注，还有一个startsWith 方法可用于过滤带有提升嵌入的字符串，它更适合您的情况；也就是说，如果过滤器按预期工作。

Answer 2

您应该覆盖值定义。见this answer

case class ID(id: String) extends scala.slick.lifted.MappedTo[String] {
   override def value: String = id
}